1. Field of the Invention
There is a continuing need for improved assay methods and reagents for the detection of an analyte in a sample. The analyte can be a member of a specific binding pair ("sbp") consisting of ligand and its homologous receptor. Exemplary of sbp members are antigens and antibodies.
In general, a sbp member complementary to the antigen will be used as an assay reagent. Other reagents used in detection assays must have particular characteristics in order to be suitable for use in the assay. When the analyte is on the surface of a particle or can be caused to bind to a particle, it is desirable to use a dye, for example a fluorescent dye, capable of staining the particle in a reproducible manner without interfering with the reaction between the analyte and its homologous sbp member.
Mammalian red blood cells carry numerous antigens some of which must be accurately identified in both patient and donor for medical procedures such as transfusions. Accurate determination of blood groups, A, B, AB, O and D (Rh.sub.o) is critically important. Also, antibodies to such blood group antigens as well as other circulating antigens can be of diagnostic interest.
Conventionally, agglutination techniques are performed on a microscope slide or in a tube with the results being assessed visually. Improved rapid, accurate and automated screening of blood is desirable in view of the critical nature of the assays performed, the labor intensity of such assays and the large numbers of samples which must be tested.